Background

Marijuana, hemp, and cannabis are common names for plants of the genus Cannabis. The term "hemp" is used for Cannabis plants that are grown for nondrug use, such as Cannabis sativa. Cannabis indica has poor fiber quality and is used to make drugs for recreation and medicine. The major differences between the two are appearance and the amount of delta-9-tetrahydrocannabinol (THC), the active ingredient of marijuana.

Cannabis sativa is widely used for recreation. It has been inhaled or taken by mouth to produce a feeling of relaxation or well-being. The plant has been studied as a potential treatment for many conditions, including chronic skin disorders, cancer-related weakness and weight loss, chronic pain, Huntington's disease, sleep disorders, eye disease, multiple sclerosis, and schizophrenia. The most significant benefits have been seen in the treatment of chronic pain and multiple sclerosis. Marijuana may help reduce eye pressure in people who have glaucoma.

The most commonly studied ingredients in marijuana are THC and cannabidiol (CBD). Research has looked at these compounds both alone and in combination. Commercially available products include dronabinol (Marinol®), nabilone (Cesamet®), THC, and CBD (Sativex®).

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older)

To treat amyotrophic lateral sclerosis (nerve cell disease), 10 milligrams of THC has been taken by mouth daily for two weeks.

To prevent nausea and vomiting caused by chemotherapy, five milligrams per meter squared of dronabinol (Marinol®) has been taken by mouth 1-3 hours before chemotherapy, then every 2-4 hours after chemotherapy, for a total of 4-6 doses daily. A dose of two milligrams of nabilone has been taken by mouth the night before chemotherapy, 1-3 hours before and after chemotherapy. A dose of 2-3 milligrams of nabilone has been taken by mouth 2-4 times daily. A dose of three milligrams of nabilone has been taken by mouth three times daily as a one-time dose, a four-day duration, and the duration of two cycles of chemotherapy. Cannabinoids have been taken by mouth over a 24-hour period as follows: 1-8 milligrams of nabilone daily as 1-4 milligrams daily, one milligram 3-5 times daily, or two milligrams 2-4 times daily or 24-50 milligrams per meter squared of dronabinol daily as 10 milligrams per meter squared 4-5 times daily, 12 milligrams per meter squared twice daily, or 15 milligrams twice daily. A dose of one milligram of nabilone has been taken by mouth 8-12 hours before chemotherapy, followed by 0.5-2 milligrams of nabilone 2-3 times daily after chemotherapy, depending on body weight. A dose of 10 milligrams per meter squared of THC has been taken by mouth two hours before and four, eight, 16, and 24 hours after chemotherapy. Cannabinoids have been injected into the muscle over the course of 24 hours in the form of 0.5-1 milligrams of levonantradol three times daily.

To treat atopic dermatitis (itchy, scaly skin rashes), hemp seed oil has been taken by mouth for 20 weeks.

To increase appetite in people with cancer, 2.5 milligrams of THC has been taken by mouth with or without one milligram of CBD for six weeks.

To treat chronic pain, cannabinoids have been taken by mouth in the form of capsules or sprayed into the mouth as THC, benzopyranoperidine (BPP), cannabidiol (CBD), nabilone, dronabinol, or synthetic nitrogen THC analogs (NIB), with doses of 2.5-20 milligrams for an average of 25 days. Cannabis-based medicines have been used for 1-6 weeks. Ajulemic acid has been used for one week. Doses of nabilone of 0.25-2 milligrams have been used daily for 4-6 weeks. Doses of smoked cannabis of 1-9.4 percent have been used for six hours to 14 days. Cannabis has been smoked 3-4 times daily for five days. Doses of dronabinol of 10-20 milligrams have been used daily for six hours to six weeks. In people with cancer, 5-20 milligrams of delta-9-THC has been taken by mouth daily, as have the following doses: 2-8 milligrams of nabilone by mouth daily; 0.25-1 milligram of nabilone by mouth daily for four weeks; 1-2 milligrams of nabilone twice daily for a year; 1-2 milligrams of nabilone twice at an eight-hour interval; and 0.5 milligrams of nabilone twice daily for seven days, followed by two milligrams daily for three weeks. A dose of 0.5-1 milligrams of nabilone has been taken twice daily. A dose of 10 milligrams of THC has been taken by mouth, increasing to a maximum tolerated dose for six weeks. A mouth sprayhas been used in divided doses of 2.5-120 milligrams for two weeks. Doses of Sativex® have been sprayed into the mouth, up to 48 sprays daily, for 1-2 weeks, then 10-15 sprays daily, or 4-8 sprays, with eight being the maximum one-time dose or within a three-hour period.

To improve appetite in people with cystic fibrosis (mucus buildup in the organs), a dose of 2.5 milligrams of dronabinol has been taken by mouth, increasing to a maximum of 10 milligrams daily for 1-6 months.

To treat dementia, 2.5 milligrams of dronabinol has been taken by mouth twice daily for six weeks.

To treat eating disorders, 7.5-30 milligrams of THC has been taken by mouth daily for four weeks.

To treat epilepsy, 200-300 milligrams of CBD has been taken by mouth daily for up to 4.5 months.

To improve fatty acid status, hemp seed oil has been taken by mouth.

To treat movement problems caused by Huntington's disease, 1-2 milligrams of nabilone has been taken by mouth daily for five weeks. A dose of 10 milligrams per kilogram of CBD has been taken by mouth daily for six weeks.

To treat sleep disorders, 40-160 milligrams of CBD has been taken by mouth.

To treat multiple sclerosis symptoms, 2.5 milligrams of dronabinol (Marinol®) has been taken by mouth daily, increasing to a maximum of 10 milligrams daily for three weeks. A dose of 15-30 milligrams of cannabis extract capsules has been taken by mouth in five-milligram increments, based on tolerance, for 14 days. Cannabis extracts, including Cannador®, have been taken by mouth for 2-4 weeks. Cannabis plant extracts containing 2.5-120 milligrams of a THC-CBD combination have been taken by mouth daily for 2-15 weeks. A mouth spray (Sativex®, containing 2.7 milligrams of THC and 2.5 milligrams of CBD) has been used at a dose of 2.5-120 milligrams in divided doses for up to eight weeks. Eight sprays within any three hours, up to 48 sprays in a 24-hour period, have been used. Sativex® has been sprayed into the mouth for 6-14 weeks.

As a nutritional supplement, 15-30 milliliters of hemp oil has been taken by mouth daily.

To treat schizophrenia, 40-1,280 milligrams of CBD has been taken by mouth daily for up to four weeks.

To treat Tourette's syndrome, gelatin capsules containing 2.5-10 milligrams of THC have been taken by mouth as a single dose. A dose of 2.5 milligrams of THC has been taken by mouth daily, increasing to 10 milligrams daily in 2.5-milligram intervals over a four-day time period for six weeks.

To treat rheumatoid arthritis, up to six sprays of Sativex® have been used once daily 30 minutes before bed for five weeks.

To treat glaucoma (increased eye pressure), a single dose of five milligrams of THC has been placed under the tongue. A dose of 20-40 milligrams of CBD has been placed under the tongue as a single dose; however, 40 milligrams appeared to increase eye pressure.

Children (under 18 years old)

There is no proven safe or effective dose for marijuana in children.

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Chronic pain

Marijuana has been studied for the treatment of chronic pain. It has been used in people whose pain did not respond to other drugs such as narcotics. Cannabis-based products like Sativex® are used to treat different types of pain, such as pain from cancer or multiple sclerosis. It is approved in Canada and many parts of Europe. In the United States, it is being studied in people who have cancer-related pain. Other cannabis-based products, such as the U.S. Food and Drug Administration (FDA)-approved dronabinol (Marinol®), are also being studied.

B

Multiple sclerosis

Marijuana has been studied for the relief of multiple sclerosis symptoms, such as nerve pain, muscle spasms, and urinary disorders. The active ingredients have effects on the central nervous system and immune cells.

C

Amyotrophic lateral sclerosis (nerve cell disease)

Current studies show that THC may lack benefit in people who have amyotrophic lateral sclerosis. More research is needed.

C

Appetite stimulant

Current studies show that cannabis-based therapy may lack benefit on weight loss and anorexia related to cancer. Early studies suggested that marijuana may improve appetite in people who have cystic fibrosis (mucus buildup in the organs) and AIDS. More research is needed.

C

Atopic dermatitis (itchy, scaly skin rashes)

Hemp seed oil may help reduce symptoms of atopic dermatitis, a chronic skin disorder that causes itchy, scaly rashes. This benefit is believed to come from the fatty acids in hemp seed oil. Further research is needed.

C

Brain injuries

Marijuana has been studied for potential benefit in people with acute brain injury. However, more research is needed before conclusions can be made.

C

Chemotherapy side effects

Studies suggest that marijuana may help reduce nausea and vomiting in people undergoing chemotherapy. However, it may cause side effects such as sleepiness and changes in mood. One review suggests that marijuana may cause more side effects in children undergoing chemotherapy than other therapies. However, the effect of cannabis alone is unclear, and further research is needed.

C

Dementia

Early studies suggest that marijuana may benefit weight gain and behavior in people who have dementia. More research is needed before conclusions can be made.

C

Eating disorders

In patients with eating disorders THC had a lack of effect on weight, caloric intake, and psychiatric assessment. Further research is required.

C

Epilepsy

Early studies suggest that marijuana taken with antiseizure drugs may lower seizure risk in people with epilepsy. However, the evidence is limited. More research is needed on whether marijuana may be effective in treating epilepsy.

C

Glaucoma (high eye pressure)

People who have glaucoma have high pressure in the eye, which may lead to optic nerve damage and vision loss. Some studies suggest that THC may lower eye pressure, while CBD may lack benefit or actually increase pressure. More research is needed to understand the possible role of marijuana in glaucoma treatment.

C

Huntington's disease (nerve cell death in brain)

Symptoms of Huntington's disease include impaired brain function and jerky body movements. Early research suggests that CBD may lack effect on movement problems caused by Huntington's, although the marijuana-based drug nabilone may have benefits. More studies are needed in this area.

C

Neuromuscular disorders

Marijuana has been studied in the treatment of symptoms of nerve and muscle disorders. Researchers looked for possible benefits on appetite, saliva production, mood, muscle health, and sleep. More research is needed before conclusions can be made.

C

Quality of life

There is some controversy over the use of marijuana in people who have cancer or other long-term illnesses. It has been studied for increasing appetite, treating stomach problems, improving mood and sleep, and reducing pain. More research is needed before conclusions can be made.

C

Rheumatoid arthritis

Limited research suggests that Sativex® may reduce pain and improve sleep quality in people who have rheumatoid arthritis. More research is needed.

C

Schizophrenia

Early research suggests that CBD may lack effect in people who have schizophrenia. Other research reports that cannabis users may have better brain function than nonusers. However, long-term use of cannabis has been linked to a higher risk of psychiatric problems. These include bipolar disorder, anxiety, suicidal thoughts, depression, delusions, hallucinations, aggression, and lack of motivation or energy. More research is needed.

C

Sleep disorders

Limited research suggests that CBD may help people who have problems sleeping. However, more studies are needed before conclusions can be made.

C

Tourette's syndrome (brain disorder causing tics)

Some research reports that marijuana may improve some symptoms of Tourette's syndrome. However, significant benefit over placebo is lacking for tics and other symptoms. More research is needed in this area.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Interactions

Interactions with Drugs

Marijuana may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Marijuana may affect blood sugar levels. Caution is advised when using medications that may also affect blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

Marijuana may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be increased in the blood and may cause increased effects or potentially serious adverse reactions. People using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

Marijuana may increase the amount of drowsiness caused by some drugs. Examples include benzodiazepines such as lorazepam (Ativan®) or diazepam (Valium®), barbiturates such as phenobarbital, narcotics such as codeine, some antidepressants, and alcohol. Caution is advised while driving or operating machinery.

Interactions with Herbs and Dietary Supplements

Marijuana may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.

Marijuana may affect blood sugar levels. Caution is advised when using herbs or supplements that may also affect blood sugar. Blood sugar levels may require monitoring, and doses may need adjustment.

Marijuana may cause low blood pressure. Caution is advised in people taking herbs or supplements that lower blood pressure.

Marijuana may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of other herbs or supplements may become too high in the blood. It may also alter the effects that other herbs or supplements possibly have on the P450 system.

Marijuana may increase the amount of drowsiness caused by some herbs or supplements.

Marijuana may also interact with anabolic steroids, anticancer herbs and supplements, antioxidants, antiseizure herbs and supplements, barbiturates, benzodiazepines, central nervous system depressants, corticosteroids, dopamine antagonists, fertility herbs and supplements, herbs and supplements that may affect blood vessel width, herbs and supplements that may affect the immune system, herbs and supplements that may be toxic to the liver, herbs and supplements that may improve breathing or treat lung disorders, herbs and supplements that may increase appetite, herbs and supplements that may treat heart disorders, herbs and supplements that may treat nausea and vomiting, herbs and supplements that may treat nervous system disorders, herbs and supplements that may treat psychiatric disorders, herbs and supplements that may treat retrovirus infections (HIV), herbs and supplements that may treat skin disorders, herbs and supplements that may treat stomach disorders, hormonal herbs and supplements, nicotine, nonsteroidal anti-inflammatories, opioid receptor antagonists, pain relievers, p-glycoprotein-regulated herbs and supplements, phytoestrogens, and synthetic cannabinoids.

Methodology

This information is based on a systematic review of scientific literature and was peer-reviewed and edited by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Avoid if allergic or sensitive to cannabinoids or to plants of the Cannabaceae family. Asthma, hives, pink eye, and runny or stuffy nose have been reported.

Side Effects and Warnings

Cannabinoids are likely safe when used for specific conditions at the recommended doses for the recommended amount of time.

Side effects have mostly been linked to THC, the active ingredient in Cannabis sativa. Dizziness is a common side effect. Marijuana may have effects on almost every organ system in the body, including the central nervous, heart, endocrine, and immune systems.

Use cautiously with alcohol. Combining alcohol and CBD may cause significantly low blood alcohol levels compared to alcohol alone, though similar effects may occur.

Marijuana may increase the risk of bleeding. Caution is advised in people with bleeding disorders or those taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.

Marijuana may affect blood sugar levels. Caution is advised in people with diabetes or blood sugar problems, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood sugar levels may need to be monitored by a qualified healthcare professional, including a pharmacist, and medication adjustments may be necessary.

Marijuana may cause low blood pressure. Caution is advised in people who have blood pressure disorders or those taking drugs or herbs and supplements that lower blood pressure.

Use cautiously in people who have liver disease or those using agents toxic to the liver.

Use cautiously in people who are taking barbiturates, antipyrine, or central nervous system (CNS) depressants.

Marijuana may interfere with the way the body processes certain agents using the liver's cytochrome P450 enzyme system. As a result, the levels of these agents may be increased in the blood and may cause increased effects or potentially serious adverse reactions. People using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.

Use cautiously in people who are on estrogen therapy.

Use cautiously in people who have immune disorders or those taking agents that may affect the immune system.

Use cautiously in people who are taking p-glycoprotein-regulated drugs.

Use cautiously in people who have a history of drug abuse or addiction. Marijuana may be addictive.

Use cautiously in people who have or are at risk of eye problems. Marijuana may cause eye problems and dry eyes, and it may increase eye pressure.

Use cautiously when consuming foods or supplements that contain cannabis seeds or oil. These products may contain a high level of THC that may trigger a positive drug screen.

Use cautiously in people who are at risk of seizure or those using antiseizure drugs. Marijuana may cause seizures.

Use cautiously in people who have or are at risk of heart disease. Marijuana may cause abnormal heartbeat, disrupted blood flow to organs (kidney, spleen), heart attack, and heart failure.

Use cautiously in people who have learning disabilities or attention-deficit hyperactivity disorder (ADHD). Marijuana may cause problems with attention, learning, memory, organization, planning, problem solving, and other brain functions.

Use cautiously in people at risk of skin problems. Marijuana may cause hives, patches in the mouth, and skin itching.

Use cautiously in people with stomach disorders. Marijuana may cause stomach problems such as a bad taste, burning or swelling tongue, diarrhea, dry mouth, increased appetite, indigestion, mouth ulcers, nausea, pain, and vomiting.

Use cautiously in people who have or are at risk of musculoskeletal disorders. Marijuana may cause bone problems, increased risk of side effects linked to musculoskeletal or connective tissue disorders, falls, muscle problems (pain, twitching, or weakness), numbness, recurrence in multiple sclerosis, reduced coordination, restlessness, and speech disorders.

Drowsiness or sedation may occur. Use caution if driving or operating heavy machinery.

Use cautiously in all otherwise healthy people who are not taking any medications. Marijuana may cause disorientation, dizziness, headaches, fatigue, a feeling of intoxication, lightheadedness, and reduced attention.

Use cautiously in people who have or are at risk of ear problems. Marijuana may cause ear problems.

Avoid if allergic or sensitive to cannabinoids or to plants of the Cannabaceae family. Asthma, hives, pinkeye, and runny or stuffy nose have been reported.

Avoid in women who are pregnant, breastfeeding, or trying to get pregnant. Marijuana may have serious risks and may cause low birthweight or abnormalities in the baby.

Avoid long-term use in people who have or are at risk of lung problems, such as asthma or byssinosis (a disease caused by breathing dust). Marijuana may cause bronchitis, coughing, lung cysts, phlegm, reduced lung density, and wheezing.

Avoid using cannabis products that have been obtained illegally. These products may contain unknown and possibly harmful ingredients, such as the animal tranquilizer PCP.

Avoid injecting cannabis into the veins. Cannabis sativa may be extremely toxic.

Avoid using in children or adolescents. Marijuana may affect brain development in the young.

Avoid using in people who have or are at risk of mental illness. Marijuana may cause anxiety and psychotic-like symptoms. It may also increase the risk of aggression, bipolar disorder, delusions, depression, hallucinations, lack of energy or motivation, and suicidal thoughts.

Avoid using before driving motorized vehicles. Marijuana may increase the risk of collision, and when combined with alcohol, it may affect alertness and driving performance.

Pregnancy and Breastfeeding

Avoid using marijuana in women who are pregnant, breastfeeding, or trying to get pregnant. Research strongly suggests that marijuana may have serious risks for the child, including abnormalities, cancer, development problems, increased leukemia risk, low birthweight, and reduced attention skills. Cannabis may affect the mother's judgment and ability to care for the child, and it should not be smoked around infants or children. Cannabis may be passed to babies through breast milk.

Selected references

Armstrong MJ and Miyasaki JM. Evidence-based guideline: pharmacologic treatment of chorea in Huntington disease: report of the guideline development subcommittee of the American Academy of Neurology. Neurology 8-7-2012;79(6):597-603.

Hjorthoj CR, Hjorthoj AR, and Nordentoft M. Validity of Timeline Follow-Back for self-reported use of cannabis and other illicit substances--systematic review and meta-analysis. Addict.Behav. 2012;37(3):225-233.

Yucel M, Bora E, Lubman DI, et al. The impact of cannabis use on cognitive functioning in patients with schizophrenia: a meta-analysis of existing findings and new data in a first-episode sample. Schizophr.Bull. 2012;38(2):316-330.

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